As disclosed in Japanese Publication for Examined Patent Application (Tokukohei) No. 3-42543, 4-31871 and 4-37425, double-side image forming apparatuses such as copying machines and laser printers capable of producing image on both sides of a sheet based on image data stored in a memory device are conventionally known. In a double-side image forming apparatus of this type, first, an image is formed on one of the sides of a sheet by an image forming section based on image data which is to be printed, for example, on the back side and read out from the memory section. Second, the sheet passes through a reversing transport path, and is supplied again in a reversed state to the image forming section. Then, an image is formed on the other side of the sheet based on image data to be printed on the front side.
In order to repeatedly operate the image forming section in the double-side image forming apparatus, images are first formed on one of the sides of the respective sheets successively, and the sheets carrying the images on one side thereof are temporarily held in the reversing transport path. Then, the sheets carrying the images on one side thereof are fed one by one from the reversing transport path so as to form images on the other side of the sheets. This structure increases the processing speed when performing image forming operations successively. In order to carry out the image forming operations at high speeds through these steps, there is a need to arrange a long reversing transport path.
However, in the conventional double-side image forming apparatus, if a long reversing transport path is arranged by simply increasing the length thereof, it is necessary to curve the reversing transport path. With this arrangement, the transport path includes many curved sections. As a result, the structure of the double-side image forming apparatus is complicated and the size thereof is increased.
Japanese Publication for Examined Patent Application (Tokukohei) No. 3-42543 discloses two reversing transport paths. In this structure, each of the reversing transport path has a turnaround section for reversing the leading edge and trailing edge of a sheet with respect to a transporting direction. Thus, the apparatus of JP 3-42543 has a complicated structure. In addition, in a conventional structure in which sheets carrying images on one side thereof are temporarily stored in an intermediate tray and then fed one by one from the intermediate tray so as to form images on the other side of the sheets, the following two problems arise. One problem is a complicated structure and a large size of the apparatus that are caused by a pickup roller provided for feeding the sheets from the intermediate tray. The other problem is a lowering of the processing speed that is caused by feeding sheets one by one from the intermediate tray for forming images on the other side of the sheets.